Research Briefs
the feed does not cause pathological changes in the liver, muscles and other organs of the experimental fi sh, and no other negative effects were determined.
Aquaculture Nutrition
Volume 20, Issue 2 Evaluation of different starch sources in extruded feed for Atlantic salmon
K AH-HEN, G LEHNEBACH, R. LEMUS- MONDACA, L ZURA-BRAVO, P LEYTON, A VEGA-GÁLVEZ AND F FIGUEROLA
The aim of the experiment was to investigate the effect
of partial or total substitution of wheat fl our with oat meal and tapioca starch in extruded salmon feed. A mix- ture design (simplex centroid mixture design) was used to analyse the effect of starch source on physical quality of extruded feed. Physical quality of the extruded feed was evaluated as cohesiveness, pellet density, axial and radial expansion, durability, hardness, strain at rupture and elastic modulus. Starch sources affected behaviour of the diet formulations during extrusion and caused changes in the physical properties of the extruded products. Signifi cant correlations (P < 0.05) between physical properties and weight fraction of the starch sources allowed the establishment of predictive models. The inclusion of oat meal and tapioca starch in the diet gave extruded feed with a higher porosity and lower oil absorption capacity. The mechanical properties of the extruded feeds were signifi cantly different from each other, most likely due to
the complex nature of texture formation with respect to process parameters and properties of ingredients.
The infl uence of different dietary oil qualities on growth rate, feed utilization and oxidative stress in Atlantic cod
MA KJÆR, IA AURSNES, GM BERGE, M SØRENSEN, Y MARCHENKO, T GJØEN AND B RUYTER
The aim of our study was to investigate the effects of
dietary oils, with different degrees of oxidative stability, on growth performance, lipid and fatty acid (FA) composition, oxidative stress status and health parameters of Atlantic cod. The dietary oils were a traditional fi sh oil (FO), a FO and rapeseed oil blend (FO-RO, 1:1), or two salmon oil (SO) qualities with low (SO-L) or high (SO-H) level of oxidation products. Fish (479 g) were fed one of the four diets for 112 days (800 g). No signifi cant differences in growth rate, feed effi ciency or morphology of the intes- tine were found. However, there was a tendency to higher thiobarbituric acid reactive substance values in plasma and liver in the FO and SO groups than in the FO-RO group, although only signifi cant for the FO group in plasma. There was also a tendency to reduced activities of catalase and SOD in the FO and SO groups. An increase in transcripts related to oxidative stress in the liver and heart was obvious. The FA composition of liver refl ected the FA composition of the diet, with lowest n-3 FA percentage in the FO-RO group, intermediate percentage in the SO groups and highest percentage in the FO group. FF
Oregano oil acts as a growth promoter for yellowtail tetra
Yellowtail tetra
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28 Untitled-2 28
www.fishfarmer-magazine.com TACKLING SEA LICE AT THE INSTITUTE OF AQUACULTURE
Stirling research ROUND UP
S Stirling scientists tackle global sea lice problem Hungarian Aquaculture
ea lice are naturally occurring obligate crusta- cean ectoparasites of salmon that continue to be one of the most costly and challenging fi sh health issues for the salmon farming industry, with
Scotland alone spending over £30 million per year on mitigation. Despite the continued focus of the aquacul- ture industry on the use of integrated pest management, alternative approaches are urgently required. The Institute of Aquaculture (IoA) is at the forefront of the battle against sea lice, with research projects on all main strategies, including the deployment of cleaner fi sh, the development of a vaccine, studies on host/parasite resistance designed to identify the parasite’s weak spots and the screening/development of novel products to re- duce sea lice burdens. Professor Herve Migaud, Director of Research at the IoA, commented: ‘These projects dem- onstrate the leading position occupied by the Institute in supporting the Scottish aquaculture sector and underline our strong commitment to solving current problems in sustainable aquaculture in the UK and worldwide.’
WRASSE - A BIOLOGICAL CONTROL The cohabitation of cultured native cleaner-wrasse species with salmon stocks is widely considered as one of the most environmentally friendly and sustainable solu- tions to pest management. This sustainability is nonethe- less only achievable if the wrasse are farmed rather than wild-caught. The farming of wrasse is currently in its rela- tive infancy, with limited knowledge of their reproductive physiology, spawning behaviour, larval development and general performance in captivity. Leading Scottish salmon producers, Marine Harvest Scotland (MHS) and Scottish Sea Farms Ltd (SSF), and scientists from the Institute of Aquaculture (IoA) Reproduction & Genetics team have been recently awarded co-funding of £2.1m from the Technology Strategy Board to support their collaborative wrasse initiative. John Webster, Technical Director of the SSPO, says: ‘We are delighted that Scottish salmon farm- ing has attracted TSB funding for a project designed to further improve the industry’s sustainability. The prospect of biological control of sea lice through the use of cleaner wrasse is exciting and promising.’ The project started in January 2012 with the aim of developing the technolo- gies to breed and grow commercially viable numbers of wrasse in tanks and to deploy in the salmon industry. Benefi ting from extensive expertise in aquaculture
ventures and in the use of wrasse as a biological control against sea lice, the industrial partners are currently run- ning a dedicated wrasse hatchery in University of Stirling premises at Machrihanish (formerly Machrihanish Marine Farm Ltd), presently holding over 1000 ballan wrasse broodstock under different light and temperature re- gimes. The project is supported by two dedicated IoA sci- entists: Bridie Grant (PhD student) and Dr Eric Leclercq (Post-Doctoral Research scientist) under the supervision of Professor Herve Migaud and Dr Andrew Davie. Achievements in 2012 include: improved spawning quan- tity and quality; refi nement of larval rearing protocols; the testing of custom-designed wrasse diets (in collaboration with fi sh feed companies); increased understanding of sex identifi cation; and manipulation, stress response, behav-
www.fishfarmer-magazine.com THE Crown Estate is calling for nominations and entries for 06/03/2013 11:03:53 Untitled-2 16 Hungary for success Wales - mussels Thomas Shellfish
– pioneering rope mussel farming in Wales
Opposite: Wrasse broodstock at
iour and wild wrasse population dynamic and genetics. One of the most important tasks during this fi rst year was to confi rm the effi ciency of wrasse in removing sea lice from salmon. The delousing effi ciency of wild wrasse in sea cages is
well documented across Scotland and Norway. However, this is not the case of their hatchery counterparts that have been reared on dry pellets. A preliminary trial at Machrihanish Marine Environmental Research Laboratory (MERL) assessed the performance of cohabiting hatch- ery-reared ballan wrasse (c30g in weight) in delousing Atlantic salmon (c150g in weight). The experiment tested two wrasse/salmon ratios (6% or 12% wrasse by number) with 50 salmon (± 7.5 lice / salmon). The trial proved to be highly successful, with the total sea lice burden being reduced by 86% and 98% (6% and 12% treatments, respectively) following 40h of cohabita- tion with both gravid female and adult/pre-adult stages preyed upon (Figure 1).
VACCINE – A NEW WEAPON IN THE WAR One alternative to the use of therapeutic medicines
would be the development of an effi cacious vaccine, pro- viding long-term protection. Such a vaccine would
Machrihanish wrasse hatchery (P Featherstone) Above: Male and female sealice (W Roy) Figure 1: Average sea- lice count per salmon (15 salmon assessed / treatment / tank) at the start of the experiment (0h) and following 40h of cohabitation with 6% or 12% ballan wrasse (30g, hatchery-origin) in 600 L tanks at a water temperature of 13.5°C (Migaud H and Leclercq E)
Colin Thomas’ mussel barge, the Carpe Diem, on station in Queen’s Dock
SUCCESS Hungary for
CASTING AN EYE ON EASTERN EUROPE
TIBOR FELEDI, GERGO GYALOG, ANDRAS RÓNYAI AND LASZLO VÁRADI RESEARCH INSTITUTE FOR FISHERIES, AQUACULTURE AND IRRIGATION (HAKI), SZARVAS, HUNGARY
Historically hatchery- reared wrasse have been less effective
Figure 1 28 16
Combined extensive
and intensive systems are increasingly popular
with a yearly production of 12-14,000 tons, accounting for 85-90 per cent of the volume. Changes in annual production mainly come from the fact that most pond farmers use traditional low intensity (extensive or semi-intensive) technologies, characterised by strong reliance on natural food production, thus yearly harvests are subject to weather conditions. This kind of fi sh farming activity is often considered to be the oldest in Europe, dating back to Medieval times, and is considered a cultural heritage in certain regions of Central and Eastern Europe. Typical fi sh ponds are earthen enclosures and cereals are applied as supplemen- tary feed to natural food, contributing to 30-60% of the biomass gain, depending on the level of farming intensity.
T
otal annual aquaculture production in Hungary varies between 14,000 and 16,000 tons. As in most Central and Eastern European countries, pond culture is the most important subsector,
Fish yields range from 500-1,000 kg ha-1 year-1 in extensive technologies to 1,000 – 2,000 kg ha-1 year- 1 in semi-intensive technologies. These plankton and cereal-based traditional technologies do not allow the production of valuable predatory species – 95-98% of the biomass gain originates from the growth of common carp (75-80%) and Asian carps. Carnivorous fi sh are only used in these technologies to control undesirable fi sh species, as direct feeding with pellets is not effi cient in polyculture. Although this way of farming can be regarded as a resource-saving, environmental-friendly production, numerous factors have challenged its economical sustain- ability. Rising fi xed costs, deteriorating market position of carps (demand shifting toward predators) and increasing bird predation have adverse effects on profi tability of low-intensity technologies. However, two distinct pond culture development models show themselves adaptable to survive: (i) creating a multifunctional farming model and generating income from angling, bird watching and tourism; (ii) applying intensive technologies that rely almost exclusively on for- mulated feeds (in combination with of the use of smaller ponds or cages in ponds) and cutting the fi xed costs per kg fi sh by increasing yields to 5-15,000 kg ha-1 year-1.
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Probably, as always, the best path to follow lies between the extremes: integration of certain elements of the two models creates a good opportunity for combined extensive systems. Intensive tank aquaculture accounts for a yearly produc- tion of 2,000 tons in Hungary (10-15% of total aquac- ulture). Flow-through systems using geothermal water are used for North African catfi sh (Clarias gariepinus X Heterobranchus bidorsalis) farming, producing some 1,800 tons yearly. The production of this species is a success story of Hungarian fi sh culture. The research work started in 1984 and nowadays Hungary is the second largest catfi sh producer in Europe. Caviar-end sturgeon farming in recirculation systems (RASs) is practised in 5-6 farms, producing 50-80 tons of meat and 2-3 tons of roe annually. Cold water aquaculture is not signifi cant in Hungary, three farms produce some 30-60 tons of trout annually. Barramundi is produced in RAS and European catfi sh (Silurus glanis) is produced in cages in one farm.
R&D AND INNOVATION
Hungary is one of the most active participants in R&D projects of the EU’s 6th and 7th Framework Programs,
www.fishfarmer-magazine.com THE Crown Estate is calling for nominations and entries for 06/03/2013 10:56:33
mainly through the activity of the Research Institute for Fisheries, Aquaculture and Irrigation (HAKI). HAKI is an important participant in EU projects, with components aimed at the development of pond fi sh farming technolo- gies and the breeding of productive and disease-resistant common carp varieties – such as Sustainaqua, Aquamax and Eurocarp. In Hungary, just like in other Eastern Euro- pean countries, the great challenge is how to make con- ventional pond fi sh production viable, taking into account the increasing competition for freshwater resources and the changing market needs. As a result of these recent R&D projects, new systems and technologies are available for practical application. In combined intensive and extensive (CIE) systems high val- ue species are produced intensively in a small production unit, while the excess nutrients of the intensive system
Opposite page: paddlefish have great potential. Clockwise from top left: the recirculation system at HAKI; selecting carp broodstock; producing African catfish using geothermal water; a striped bass hybrid
T 16 20
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involved when my father made the move into rope farming, and now oversee the administra- tion and fi nance, and direct the general strategy of the business. My previous experience working in oil and gas trading in the City was good training for dealing with the level of bureaucracy involved in the mussel farming world!’ she explained.
INVESTMENT
Once on board, Melony put to- gether an investor package, which brought in some enthusiastic shareholders, and Colin set about trialling the different rope and net production systems on the market. ‘We got the best performance
NEW PROJECT GIVES DOCKS A POST-INDUSTRIAL LEASE OF LIFE BY NICKI HOLMYARD
homas Shellfi sh, a fam- ily-run business based in South Wales, is breaking new ground by farming
mussels in the Queen’s Dock in Swansea. Colin Thomas, a fi sherman for
more than 40 years, had been involved in the seabed mussel industry for the past decade, but
three years ago realised his ambi- tion to set up trials in the dock using rope culture. ‘I had looked at the vast expanse
of unused water there for a long time and it wasn’t until I sat down
with my wife and daughters and they encouraged me to “go for it” that we put together a proper business plan and started to de- velop the idea,’ said Colin. Swansea docks once handled vast
www.fishfarmer-magazine.com 12/09/2013 12:26:58
quantities of coal, petrochemicals and metals from local industries, including 70% of the world’s copper resource. Today it is a redevelopment area, which offers a clean, sheltered environment for its newest industry. However, its history caused a lot of scepticism when Colin fi rst raised the idea of producing food in the docks, so the fi rst thing
he put in place was a testing and monitoring project in conjunction with an environmental consult- ant and Swansea University. This looked at the salinity and tem- perature profi les of water samples collected from different depths and locations, and analysed them for dissolved oxygen, dissolved nu- trients, suspended organic carbon, nitrogen and chlorophyll.
www.fishfarmer-magazine.com 020-023_ff09.indd 21
‘We have no sewage outlets in the area and the tests all showed that the water quality is excellent and highly suitable for supporting mussel production, which proved what our instincts told us,’ stated Colin.
Daughter Melony, fi nance direc- tor of the operation, works from Kazakhstan, but is moving back to the UK in the autumn. ‘I got
from Quality Equipment ropes, which are made in New Zealand, and found its group director Joe Franklin highly knowledgeable and helpful,’ he said. ‘The ropes have a high surface area, which is very good for collecting spat and also negates the use of pegs for ongrowing, which enables us to introduce a high level of mechani- sation.’
Armed with confi dence from the trials, Colin set about building out the farm, which currently compris- es 12 headlines, each 220 metres long, buoyed up with Gem Plastic fl oats from Ireland. The lines are 5 metres apart and support a con- tinuous rope system, which is tied
21 12/09/2013 12:27:40 Thomas Shellfish – pioneering rope mussel farming in Wales
Tests all showed that the water quality is excellent
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